X-ray inspection apparatus, X-ray inspection system, and X-ray inspection method

Abstract

An X-ray inspection apparatus includes a transport unit configured to transport an article, an electromagnetic wave irradiation unit configured to irradiate the article with a first electromagnetic wave in a first energy band and a second electromagnetic wave in a second energy band, an electromagnetic wave sensor configured to detect the first electromagnetic wave and the second electromagnetic wave, and a control unit to which a detection result is input. The control unit is configured to generate a first transmission image based on a detection result of the first electromagnetic wave and a second transmission image based on a detection result of the second electromagnetic wave, to perform image processing including a subtraction process on the first transmission image and the second transmission image, and to determine whether or not a foreign material is included in the article on the basis of a difference image.

What is claimed is: 
     
         1 . An X-ray inspection apparatus comprising:
 a transport unit configured to transport an article;   an electromagnetic wave irradiation unit configured to irradiate the article with a first electromagnetic wave in a first energy band and a second electromagnetic wave in a second energy band higher than the first energy band;   an electromagnetic wave sensor configured to detect the first electromagnetic wave and the second electromagnetic wave emitted to the article; and   a control unit to which a detection result of the electromagnetic wave sensor is input,   wherein the control unit is configured to:
 generate a first transmission image based on a detection result of the first electromagnetic wave and a second transmission image based on a detection result of the second electromagnetic wave; 
 perform, after specifying a gradation corresponding to a largest number of pixels from a luminance distribution related to a background other than the article displayed in the first transmission image and the second transmission image, image processing including a subtraction process on the first transmission image and the second transmission image based on the gradation that has been specified; and 
 determine whether or not a foreign material is included in the article on the basis of a difference image obtained by the subtraction process. 
   
     
     
         2 . The X-ray inspection apparatus according to  claim 1 ,
 wherein the image processing further includes:
 a look-up table (LUT) generation process of generating an LUT used to match a brightness of the first transmission image with a brightness of the second transmission image, on the basis of first data indicating the number of pixels for each gradation in the first transmission image and second data indicating the number of pixels for each gradation in the second transmission image; 
 an LUT correction process of correcting at least a portion of the LUT, directly or indirectly using the luminance distribution; and 
 an image correction process of correcting the brightness of the first transmission image using the corrected LUT, and 
   wherein the subtraction process is performed on the first transmission image after the image correction process and the second transmission image.   
     
     
         3 . The X-ray inspection apparatus according to  claim 2 ,
 wherein the control unit is configured to:
 specify a second gradation which is lower than the gradation and is closest to the gradation among gradations corresponding to a smallest number of pixels from the luminance distribution in addition to the gradation; and 
 correct at least a part of the LUT from the gradation to the second gradation. 
   
     
     
         4 . The X-ray inspection apparatus according to  claim 3 ,
 wherein the control unit is configured to correct between the gradation and the second gradation in the LUT so as to increase proportionally.   
     
     
         5 . The X-ray inspection apparatus according to  claim 2 ,
 wherein, in the LUT correction process, at least a part of the LUT is corrected using an LUT for correction which is generated on the basis of the luminance distribution.   
     
     
         6 . The X-ray inspection apparatus according to  claim 1 ,
 wherein the electromagnetic wave sensor includes a sensor member configured to detect X-rays in a plurality of different energy bands.   
     
     
         7 . The X-ray inspection apparatus according to  claim 1 ,
 wherein the background is a portion of a surface of the transport unit.   
     
     
         8 . The X-ray inspection apparatus according to  claim 7 ,
 wherein the luminance distribution related to the background is generated during an idle operation of the X-ray inspection apparatus in which no articles are disposed on the transport unit.   
     
     
         9 . An X-ray inspection system comprising:
 an X-ray inspection apparatus including:
 a transport unit configured to transport an article; 
 an electromagnetic wave irradiation unit configured to irradiate the article with a first electromagnetic wave in a first energy band and a second electromagnetic wave in a second energy band higher than the first energy band; and 
 an electromagnetic wave sensor configured to detect the first electromagnetic wave and the second electromagnetic wave emitted to the article; and 
   a controller to which a detection result of the X-ray inspection apparatus is input,   wherein the controller is configured to:
 generate a first transmission image based on a detection result of the first electromagnetic wave and a second transmission image based on a detection result of the second electromagnetic wave; and 
 perform, after specifying a gradation corresponding to a largest number of pixels from a luminance distribution related to a background other than the article displayed in the first transmission image and the second transmission image, image processing including a subtraction process on the first transmission image and the second transmission image based on the gradation that has been specified. 
   
     
     
         10 . The X-ray inspection system according to  claim 9 ,
 wherein the image processing further includes:
 a look-up table (LUT) generation process of generating an LUT used to match a brightness of the first transmission image with a brightness of the second transmission image, on the basis of first data indicating the number of pixels for each gradation in the first transmission image and second data indicating the number of pixels for each gradation in the second transmission image; 
 an LUT correction process of correcting at least a portion of the LUT, directly or indirectly using the luminance distribution; and 
 an image correction process of correcting the brightness of the first transmission image using the corrected LUT, and 
   wherein the subtraction process is performed on the first transmission image after the image correction process and the second transmission image.   
     
     
         11 . The X-ray inspection system according to  claim 10 ,
 wherein the controller is configured to:
 specify a second gradation which is lower than the gradation and is closest to the gradation among gradations corresponding to a smallest number of pixels from the luminance distribution in addition to the gradation; and 
 correct at least a part of the LUT from the gradation to the second gradation. 
   
     
     
         12 . The X-ray inspection system according to  claim 11 ,
 wherein the controller is configured to correct between the gradation and the second gradation in the LUT so as to increase proportionally.   
     
     
         13 . The X-ray inspection system according to  claim 10 ,
 wherein, in the LUT correction process, at least a part of the LUT is corrected using an LUT for correction which is generated on the basis of the luminance distribution.   
     
     
         14 . The X-ray inspection system according to  claim 9 ,
 wherein the electromagnetic wave sensor includes a sensor member configured to detect X-rays in a plurality of different energy bands.   
     
     
         15 . The X-ray inspection system according to  claim 9 ,
 wherein the background is a portion of a surface of the transport unit.   
     
     
         16 . The X-ray inspection system according to  claim 15 ,
 wherein the luminance distribution related to the background is generated during an idle operation of the X-ray inspection apparatus in which no articles are disposed on the transport unit.   
     
     
         17 . An X-ray inspection method comprising:
 irradiating an article which is being transported, with a first electromagnetic wave in a first energy band and a second electromagnetic wave in a second energy band higher than the first energy band;   generating a first transmission image based on a detection result of the first electromagnetic wave and generating a second transmission image based on a detection result of the second electromagnetic wave;   performing, after specifying a gradation corresponding to a largest number of pixels from a luminance distribution related to a background other than the article displayed in the first transmission image and the second transmission image, image processing including a subtraction process on the first transmission image and the second transmission image based on the gradation that has been specified; and   determining whether or not a foreign material is included in the article on the basis of a difference image obtained after the performing the image processing.   
     
     
         18 . The X-ray inspection method according to  claim 17 ,
 wherein the background is a portion of a surface of a transport unit on which the article is transported.   
     
     
         19 . The X-ray inspection method according to  claim 18 , further comprising
 generating the luminance distribution related to the background during an idle operation in which no articles are disposed on the transport unit.